Telemetering device for testing surfaces



May 23, 1950 A. F. ECKEL 2,509,135

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TELEIIETERING DEVICE FOR TESTING SURFACES Filed April 12,1945 8 Sheets-Sheet 8 l N l 'EN TOR.

W m %w/% Patented May 23, 1950 TELEMETERING DEVICE FOR TESTING SURFACES Arthur F. Eckel, Chicago, Ill., assignor to Illinois Tool Works, Chicago, Ill., a corporation of Illinois Application April 12, 1945, Serial No. 588,032

Claims. I

This invention relates to an electric telemeter, and more particularly to a telemetric system and recorder for surface testing machines.

It is an object of this invention to provide a telemetric system or recorder which is relatively simple in construction, and hence relatively inexpensive, and at the same time more rugged in character and more reliable and accurate in operation than systems and recorders heretofore known.

Telemetric recorders heretofore known have been either of the limited swing, fast response type, or of the large swing, slow response type. It is an object of this invention to provide a large swing, fast response type of telemetric recorder.

The invention, in one of its aspects, consists in the provision of a telemetric transmitter and a telemetric receiver or recorder interconnected in such manner that the instantaneous value of the force applied to the indicator or driven element of the receiver is determined by the instantaneous value of the angular difference between the position of the moving or gauging element or" the transmitter and the position of the driven or indicating element of the receiver so that the rate of movement of the last mentioned element of the receiver shall be determined by the rate of move= ment of the moving or gauging element of the transmitter, and the response time of the system substantially the same as the response time of the transmitter.

The invention further consists in the provision of a telemetric recorder having a coil of an electric generator of variable ratio transformer associated with the pen of the recorder and with the telemetric transmitter in such manner that the position of the recorder pen determines the value of the voltage generated in the coil and that voltage is employed in combination with 9, voltage generated. in a like coil of the transmitter to control the magnitude or duration of electric energy impulses supplied to opposed pen driving coils of the recorder so that the direction and instantaneous value of the force applied to the pen is determined by the direction and instantaneous value oi the angular swing of the pen, and the pen thereby caused to respond substantially instaneously to the movement of the coil of the transmitter.

v It is a further important feature of applicants invention that overswing of the pen of the recorder is resisted by the application of a dynamic braking force which is a function of the angle of pen overswing.

'Ihe. invention, in another of its aspects, consists in the provision of a telemetric recorder in which the pen is maintained at rest by instantaneously equal, and opposite forces, one of which is increased and the other decreased when movement of the pen is required, so that creepin of the pen is dynamically resisted and instantaneous response of the pen obtained.

Other and further objects and advantages of the invention will be apparent from the following description when taken in connection with the accompanying drawings, wherein:

Figure 1 is a view in perspective of an involute gear testing machine provided with a telemetrlc recorder system embodying the invention;

Figure 2 is a fragmentary enlarged view in vertical section taken substantially along the line 2-2 of Figure 1;

Figure 3 is a view in elevation, partly broken away, of the telemetric, surface gauging transmitter;

Figure 4 i a view in horizontal section taken substantially along the line 4-4 of Figure 3;

Figure 5 is a diagrammatic illustration of the pen controlling unit of the telemetric recorder system of Figures 1 and 2;

Figure 5A is a voltage wave diagram illustrating the operation of the control unit of Figure 5;

Figure 6 is an enlarged fragmentary view in vertical section taken substantially along the line 66 of Figure Figure 7 is a view in vertical section taken substantially along the line 1l of Figure 6;

Figure 8 i an enlarged fragmentary View in vertical section taken substantially along the line -i8 of Figure 6;

Figure 9 is a fragmentary, top plan view of the pen driver shown in Figures 5 to 3;

Figure 10 is a fragmentary view in horizontal section taken substantially along the line iii-4E of Figure 6;

Figure 11 is a view in perspective of the pen mounting element of the pen driver shown in Fig- -ures 5 to 10;

Figure 12 is an enlarged view in perspective of the voltage generating coil forming part of the pen driver shown in Figures 5 to 11;

Figure 13 is a diagrammatic view of a modified form of the pen controlling telemeter unit; and

Figure 14 is another modified form of the pen controlling telemeter unit.

In Figures 1 and 2 of the drawings, a telemetric recorder system embodying the invention is illustrated in association with a standard, involute tooth measuring or gear testing machine 20 which comprises a suitable base 22 upon which is mounted a slide frame 24. The frame 24 is slldablo upon horizontal ways or tracks 26 at the upper edge of the base 22.

The frame 24 is formed with a depending section 28 (Figure 2) in which is journaled a sleeve 30. The sleeve receives the tapered shank 32 of a spindle 34 having an annular flange 36 to support a disk 38 which is of an external diameter equal to the diameter of the base circle of the gear 40 to be tested. The disk 38 is detachably mounted in a suitable manner on the spindle so.

that it may be readily replaced by a similar disk of a different size corresponding to a different size gear to be tested. The spindle 34 terminates near its upper end in a conical work support center 42 which receives the lower end of the gear or work supporting spindle 44. The upper end of the spindle 44 is received by the center 46 (Figure l) of a tail stock 48 mounted for vertical adjustment on columns 50.

The base disk or cylinder 38 is coupled to the gear 40 to be tested by a lever 52 which is detachably clamped to the spindle 34. The arm of the lever is slotted, as at 54, to receive a post or rod 56 that is clamped to the lever for adjustment along the slot. The post 56 supports a vertically adjustable rod 58 that fits between the adjacent teeth of the gear 40 to be tested, as shown in Fi ure 1.

A frame 60 is slidably mounted upon the base 22 and is provided with a depending portion 62. This frame is provided with upper and lower roller bearings 84 (Figure 2) which roll upon bars 66 and 88 when the hand wheel I (Figure l) is rotated. An auxiliary frame 12 is vertically adjustable on the frame by means of a hand wheel A tooth traversing contactor 16 (Figure 2) is adjustably mounted in a lever I8 fulcrumed by a transverse pin 80 bet-ween centers 82 carried by the arms of a bracket 84 fastened to or formed integrally with the vertically adjustable frame 12. The lever 18 passes through an enlarged opening in the vertical wall of the bracket 84 and is formed at its outer end with a thrust ball 86 engaging and operating the transmitter of the pen driving telemeter unit, hereinafter to be described.

The disk 38 is urged into engagement with a frictionally effective driving bar 88, carried by the horizontally slidable frame 60, by means of a roller bearing 90 carried by a slide 92 urged by a spring 84 into engagement with the disk as the slide frame '24 is adjusted by means of a hand wheel 96. An angle indicating lever 98 (Figure 1) is frictionally clamped to the spindle and cooperates with a graduated scale I00 to indicate the angular movement of the gear or work piece during the testing operation.

In order to make a test, the frame 12 is adjusted vertically, by the hand wheel "I4, properly to position the contactor on the surface of the tooth to be tested and the hand wheel I0 is hen rotated 0 cause horizontal movement of the frame 60 and the frame I2. This causes, through the frictionally effective driving bar 88, rotation of the base cylinder 38, the spindle 34 and the gear 40. On any deviation of the tooth surface from the true involute shape, the contactor I6 is swung on the pivot 82 in one direction or the other, depending on the direction of deviation of said surface from said true shape.

The telemetric recorder system, as shown in Figures 1 and 2, comprises a recorder I02 (Figure l), a position responsive transmitter I04 (Figure 2) and a surface measuring transmitter I06 (Fig- I ures 1 and 2). The recorder I02 comprises a paper feed, telemetric receiver I08 which may comprise any suitable paper feed mechanism driven by an A. C. Selsyn motor, not shown, coupled through control unit H0 and cable II2 to the A. C. Selsyn generator II4 of the position responsive transmitter I04. The recorder I02 also comprises a pen driving telemetric receiver II6 forming with the telemetric transmitter I06 the pen driving telemeter system, the receiver I I6 being connected to the transmitter I06 through the control unit I I0 and a cable H8.

The control unit I I0 may comprise any suitable conventional system of switches, rheostats and connectors for connecting and disconnecting the telemetric transmitters to and from the telemetric receivers and for calibrating and adjusting the pen driving telemetric receiver.

As shown in Figures 3, 4 and 5, the surface measuring telemetric transmitter I06 comprises a conventional dial indicator mechanism I having its dial and pointer removed. The mechanism I20 is mounted on an arm I22 which swivels upon the axis of a stud I24 (Figure 2) mounted upon the bracket 84 so that the mechanism may be moved from one side of the thrust ball 86 of the pin T8 to the other side thereof to enable testing of both surfaces of an involute tooth.

The rotary portion of the indicator mechanism I20 comprises a shaft I28 that responds by angular movement to the displacement of a plunger I28 which is spring pressed outwardly to engage the ball end 86 of the lever 18 to maintain the contactor I6 in engagement with the surface being tested. Although the shaft I26 may be coupled to the plunger I28 in any desirable manner, the coupling may be accomplished by an offset rack I 21 formed integral with the plunger I28 and engaging a pinion I29 fixed to the shaft I26. The plunger I28 is maintained in engagement with the ball 86 by means of a spring I3I connected from the rack I21 to any convenient fixed point such as a stud I33 mounted on the upper plate I32 of the mechanism I20.

An electric generator or variable-ratio transformer I30 is mounted on the upper plate I32 of the mechanism I20 and enclosed in a casing I34 secured to the casing of the mechanism I20. The electric generator I30 comprises alternating current stator windings I36 wound on a laminated core I38 supported in any suitable manner on the plate I32 and having central core legs I48 between which is mounted, coaxially with the shaft I26, a rotor I42. The rotor I42 comprises a suitable coil I44 wound upon a core or form of insulating material secured at its lower end to a shaft I48 and at its upper end to a shaft I50.

The coil I44 is electrically connected at its opposite ends to the shafts I48 and I50. The shafts are journaled in a bracket I52. The bracket is formed of insulating material, or the shafts are journaled in insulating bushings mounted in bracket openings. Terminal screws I54 are connected to the output leads I56 and I58 (Figure 5), by wiper springs I60 which engage the shafts I48 and I50.

The shaft I48 is mechanically coupled to the shaft I26 of the mechanism I20 through a coupling sleeve I62 of insulating material. The shaft I projects through an enlarged opening in the dial plate I64 and carries a cooperating dial pointer or indicator I66. The dial plate I64 is calibrated in the same manner as the usual dial gauge so that the pointer I66, on movement of the plunger 1253, indicates positive" and negative deviations of the tooth surface from the true involute shape. An escutcheon I68 mounts a dial glass I on the casing I34.

The pen driving, telemetric receiver II6 comprises, as best shown in Figure 5, a pen driver unit or recorder I12 and a control unit or circuit I14. The pen driver unit or recorder comprises a driver section I16, mechanically connected to the pen I18 and an electric generator section I80 controlled by and responsive to the movement and position of the pen.

The pen driver section comprises two cylindrical armature coils I82 and I84 wound on, or mounted in, plastic cylinders slidably mounted on the opposite ends of a tube I86 of magnetically susceptible material press fitted or otherwise secured to the internal flange of a magnetically susceptible cylinder I88. The cylinder I88 is press fitted or otherwise secured to a permanent magnet I90 of cylindrical form, and which at its end abuts permanent magnet rings or pole pieces I92 and I94. The pole pieces I92 and I94 cooperate with the magnetically susceptible tube I86 to provide air gaps in which the armature coils I 82 and I 84 are movable by the interaction of the magnetic field created by currents flowing through the coils and the magnetic fields in the air gaps.

The coils I82 and I84 are provided with end caps I96 and I98 secured to a common shaft or rod 200 which passes through the magnetically susceptible tube I86 and projects from the end cap I98 of the coil I84. A brass rod 2%: (Figure 10) is coupled in any suitable manner to one end of the shaft 200 and is formed at its ouwr end as a rack 204 slidably mounted in a guideway formed in a bracket 208 fastened to the end wall 208 of the cylindrical end casing 2) of the pen driver section.

The end casing 210 and a like, oppositely positioned, end casing 2I2 are fastened any suit able manner tothe magnet I90 and the pole pieces I92 and I94, and are mounted in any ap propriate manner on a supporting base 2 I4. The rack 204 meshes with a gear 2I6 (Figures 6, 7 and 10) secured to a shaft 2I8 secured to and depending from a disk 220. The disk is, in turn, coupled by an insulating coupler 22?: (Figures 6 and 7) to a shaft 224 journaled in an insulating bushing 228 in a plate 228 fastened to the bracket 208.

The pen 118 is of conventional form and re: ceives its supply of ink by capillary attraction from an ink well 230, into which the inner end of the pen dips, the ink well being mounted in any convenient manner on the bracket 208. The pen is received in and soldered to the tubular end of a holder 232 fastened to a block 239 pivoted for raising and lowering on the outer end of a mounting strip 239 of a form shown in Figure 11, the strip having a bifurcated inner end portion 238 permitting passage of the coupling 222, and is fastened to the disk 220 so that the strip swings as the disk is rotated and thereby causes horizontal movement of the pen over the record sheet 240.

The stator of the electric generator or variableratio transformer section I80 comprises coils 242 (Figures 5,.1, 9 and 10) wound on a laminated iron core 244 bolted to the end casing 2I0 of the pen driver section and formed in its upper leg with an air gap in which the rotor is received. The rotor comprises a coil 246 wound upon an insulating, preferably plastic, core form 248 to which are riveted, or otherwise fastened, upper and lower end plugs 250 and 252 (Figure 12) having depending leg portions received in slots 254 in the side walls of the core form, the end plugs being secured to the core form, as by rivets or other desirable fastening means 256.

The ends of the coil 246 are electrically connected to the shaft 224 and to a shaft 258, which are molded in, or secured in other manner, to the end plus 250 and 252. The shaft 258 is journaled in an insulating bushing 260 (Figures 6 and '1) in the arm of a bracket 262 fastened to end casing section 2I0. Electrical connection is made to the shaft 258 through a wiper s ring 284 (Figures 6 and 9) fixed to a terminal strip 266 mounted between an insulating sleeve 288 and an insulating block 210 secured to the bracket 262, as by a bolt 212. Electrical connection to the shaft 224 is made through a wiper spring 214 secured to a terminal screw 216 (Figure 5) mounted in any appropriate manner on the plate 228.

The control unit or circuit I14 (Figure 5) comprises a pair of electronic, gas discharge tubes or Thyratrons 218 and 280 having their anodes or plates 282 and 284 connected in parallel, and by wire 286 to the alternating current supply line LI. The cathode 288 of the tube 218 is connected by wire 290 of cable 292 to one end of the armature coil I84 of the pen driver, the other end of this coil being connected by wire 294 of cable 292 to one end of adjustable resistor 298 a d one end of a fixed resistor 298. The other end of the adjustable resistor 298 is connected, as by wire 300, grounded as at 302, to the other alternating current supply line L2. The other end of the fixed resistor 298 is connected to the common plate lead 286. The resistors 296 and 298 constitute an adjustable voltage divider across the portion 298 01 which the tube 218 is connected in series with the pen driver coil I84.

The cathode d of the tube 280 is similarly connected by wire 306 of cable 308 to one end of the pen driving armature coil I82, the other end of which s connected by wire 8i0 of said cable to one end of an adjustable resistor 352 corre sponding to the resistor 206, and one end of a fixed resistor Sid corresponding to the fixed resistor 298. The other end of the resistor (H2 is connected to grounded wire 300, and the other end of resistor 354 is connected to the plate lead 286.

The grid 3MB of the tube 218 is capacitively coupled to the secondary 318 of an input transformer 320, the coupling comprising a condenser 322 connected in series with the secondary between the grid and the cathode of the tube, the secondary being shunted by a coupling resistor 324 and the grid being connected to the cathode by a grid resistor 326. The cathode 288 is grounded, as at 325, through condenser 321 which forms a grid biasing impedance or reactance and provides an out-or"-phase A. C. grid bias voltage, as indicated in Figure 5A, to cause the tube 218 to operate at substantially the peak value of positive plate voltage when the system is in balance.

The grid 328 of the tube 280 is similarly capacitiveiy coupled to the secondary 330 of input transformer 332 by a series condenser 334 and shunting resistors 336 and 338. The cathode 304 isgrounded, as at 331, through condenser 399, similar to the condenser 321, to provide an outof-phase A. C. grid bias voltage for the tube 280, as indicated in Figure 5A, so that this tube also operates at substantially the peak value of positive plate voltage when the system is in balance.

7; The grid biasing reactances 321 and 338 may be provided or augmented by the distributed capacity-to-ground of the secondary windings of the transformers 320 and 332, if the ground connections 325 and 331 are eliminated.

The primary windings 348 and 342 of the input transformers 320 and 332, respectively, are connected in series with the rotor coils I 44 and 248 of the telemetric transmitter and the telemetric recorder, and a phasing or balancing condenser 344. Thus, one end of each of the primaries is connected directly to the condenser 344, while the other end of the primary 342 is connected by wire 346 and wire 348 of the cable II8 to the lead I58 from the rotor coil 44, and the other end of the primary 348 is connected by wire 358, wire 352 of cable 354, rotor coil 24$, wire 356 of cable 354, wire 358, and wire sac of cable H8 to the lead I58 from the rotor coil I44.

The stator coils I36 of the transmitter I06 are connected by cable 382 to the supply lines LI and L2 and the stator coils 242 are similarly connected to their supply lines by cable 364.

The several coils of the electric generator or transformer section of the recorder and of the transmitter are so wound or connected that the output voltages of the rotor coils I44 and 248 are in phase opposition and the voltage impressed across the series circuit of the primaries 348, 342 and condenser 344 is the difierence between the output voltage of the coil I44 and the output voltage of the coil 248.

The pen driver coils are so wound or connected that one tends to move the shaft 200 in one direction and the other tends to move it in the other direction. Thus the coil supplied with the greater average current determines the direction of movement of the shaft and, hence, the direction of swing of the pen I18.

The voltages PI and P2 impressed on the plates of the tubes 218 and 280, and the grid bias voltages CI and C2, are predetermined by selection and adjustment of the resistors 298, 298, 3I2 and 3H and the condensers 321 and 339. The adjustment is preferably such that the bias voltages CI and C2 (Figure 5A) intersect the critical grid voltage curve at points F0 so that both tubes fire substantially at the mid-point of each positive half cycle of plate voltage when the output voltages of the coils I44 and 245 are zero or equal. Under these circumstances, the pulsating direct currents supplied to the driver coils I82 and I84 are instantaneously equal and the pen driving shaft 280 is, therefore, dynamically balanced and maintained at rest.

It is preferred to so orient the rotor coils I44 and 245 in respect to the needle of the transmitter and the pen of the recorder that when the needle and pen are in zero positions, the rotor coils are disposed parallel to the fiux lines of their respective stator fields. Hence, when the needle and pen are in zero position, no voltage is induced in either of these coils and the pulsating currents supplied to the pen driver coils are of equal average value and the pen is dynamically balanced in its zero position.

The transformers 320 and 332 are so connected to the grid circuits of the tubes, and the condensers 322 and 334 are so adjusted or preset, that the operating or signal voltages impressed on the grids of the two tubes are of opposite phase and either substantially in phase or substantially 180 out of phase with the grid bias voltages CI and C2. When the rotor of the transmitter is displaced with respect to the rotor oi the recorder, the signal grid voltages E! E2, or E8 and E4, are impressed on the grids of the two tubes. The resultant grid voltages VI and V2, or V3 and V4, intersect the critical grid voltage curves GI and G2 at the firing points FI and F2, or F3 and F4.

For example, let it be assumed that the rotor coil I44 is swung in a counterclockwise direction. The voltage VI impressed on the grid of the tube 218 is then the resultant of the signal grid voltage EI and the grid bias voltage CI so that it fires at the point FI in the early part of its positive half cycle while the grid voltage V2 impressed on the tube 280 is then the resultant of the signal grid voltage E2 and the grid bias voltage C2 so that tube 288 fires at the point F2 in the late part of each positive half cycle of plate voltage. A greater average current is, therefore, supplied to the coil I84 and a lesser average current supplied to the coil I82, and the shaft 208 is moved inwardly or to the left, as seen in Figure 5, to swing the pen I18 in a counterclockwise direction. If the rotor coil I44 had been instantaneously displaced a smaller angular distance, the tube 218 would have still fired in the first half of each positive half cycle of plate voltage but at a later instant, so that the average current in the coil I84' would not have been increased as much and, similarly, the average current in the coil I82 would not have been decreased as much. Hence a smaller net actuating force would have been applied to the pen driver shaft by the coils I82 and I84. When the rotor coil I44 is displaced in the opposite or clockwise direction, signal grid voltages E3 and E4 are applied to the tubes 218 and 280, respectively, and the resultant grid voltages V3 and V4 cause the tube 218 to fire at the point F3 and F4. Hence, the current in the coil I82 is now increased and the current in the coil I84 decreased so that the pen turns in a clockwise direction.

The rotor coil 246 is connected in phase opposition to the rotor coil I44, so that as it swings toward the position of the coil I44 it decreases the magnitude of the signal voltage impressed on the grids of the Thyratrons. Hence it delays the firing instant of the tube which is firing in the first half of its positive half cycle of plate voltage and advances the firing instant of the tube which is firing in the second half of its positive half cycle of plate voltage. Consequently, the net driving force exerted on the shaft 288 of the pen is decreased as the angular displacement between the needle of the transmitter and the pen of the recorder decreases.

When the pen reaches the same angular position as the needle of the transmitter, the signal voltage impressed on the grids of the tubes is reduced to zero and the currents in the driver coils become equal and the pen shaft is, therefore, dynamically balanced, and the pen forcibly held in the same position as the needle of the transmitter.

The operations of the control unit may be summarized as follows: Whenever the needle of the transmitter swings in a counterclockwise direction, with respect to the pen of the recorder, the tube 218 fires in the first part, or first of its positive half cycle of plate voltage, while the tube 288 fires in the later part, or between 90 and of its positive half cycle of plate voltage. Whenever the needle of the transmitter swings in a clockwise direction, with respect to the pen of the recorder, the tube 280 fires in 1 early part of its positive half cycle of plate voltage, while the tube 218 fires in the later part of its positive half cycle of plate voltage.

It is a features of the control unit shown in Figure that the tubes operate at substantially the mid-point of each positive half cycle when no signal voltages are impressed on the grids. This follows from the fact that the grid bias voltages intersect the critical grid voltages of the tubes at substantially the peak value of the plate voltage. However, .where maximum sensitivity is not required, the bias voltages may be made such that the tubes fire, in the absence of signal grid voltages, at other instantaneous values of plate voltage.

In lieu of the grid biasing reactances 321 and 339, the electric generator or transformer sections of the transmitter and recorder may be wound or adjusted, or suitable voltage dropping resistors and dividers employed, to create a predetermined signal voltage difference when the needle of the transmitter and the pen of the recorder are in the same angular positions.

Thus adjustable resistors 386 and 368 may be inserted in the leads to the stator coils of the transmitter and the stator coils of the electric generator section of the recorder, and voltage dividers 310 and 312 may be inserted in the out put leads from the rotor coils of the transmitter and the recorder.

If high valued resistors of the grid-leak" type are employed as the grid resistances 328 and 338, the grid biasing reactances 321 and 329 may be eliminated and the free grid potential, augmented by the negative charges electrostatically induced upon the grids and the coupling condensers during each negative half cycle of the plate voltage, relied upon to provide a D. C. bias for the tubes and cause operation of the tubes at substantially the peak value of the positive half cycle of plate voltage when no signal voltages are applied. In such case, the signal voltage also augments or reduces the D. C. bias during the negative half cycles of plate voltage and during the positive half cycles up to the instant of firing of the tubes. Hence, it has been observed, in this case, a smaller change in the amplitude of the signal voltage effects a still greater change in the firing periods of the two tubes and thereby produces a greater change in the average plate currents of the tubes for a given degree of movement of the transmitter needle. The control unit is, in this case, more sensitive to extraneous influences and shielding of components of the circuit, e. g., the transformers 320 and 332, may be required to obtain completely satisfactory operation in some installations.

, In the form of the invention shown in Figure 5, the substantially fixed phase relations of the sig nal grid voltages to the common plate voltage determine which tube fires in the first half of its positive half cycle of plate voltage and which fires in the last half of its positive half cycle of plate voltage, but the amplitude of the signal grid voltages predominantly determines the amount of the change in the firing period of each tube.

In the forms of the invention shown in Figures l3 and 14, the phase of the signal grid voltages relative to the plate voltage determines which tube fires in the first half of each positive half cycle of plate voltage, and that phase relation is varied to determine the change in the lengths of the firing periods of the tubes. Thus in the form of the invention shown in Figure 13, the telemetric transmitter :36 is provided with a shaft I48 which corresponds to the shaft 10 N8 of the telemetric transmitter I08 and is angularly shifted by a displaceable member such as plunger I28. A movable coil 314, which cooperates with a stationary coll 316, is secured to the shaft "8'. These two coils form a variable inductance or reactance 311, the inductance value of which depends on the angular position of the coil 314 relative to the coil 318. The shaft I48 is connected through an insulating coupler, 318 to a shaft 388 which carries a pointer Ill corresponding to the pointer I88 of the form shown in Figures 3 and 5. The shaft 380 also has secured to it a coil 382 which cooperates with the stationary coil 384. These two coils form a variable inductance or reactance 385, the inductance value of which depends on the angular position of the coil 382. The coils of each of the reactances 311and 385 are so wound and connected, and the positions of the rotors so fixed on their respective shafts, that angular movement of the shafts in one direction causes an Figures 5 to 12, and this shaft has secured to it a coil 3% which forms, with a cooperating stationary coil 388, a variable inductance or reactance 383. The shaft 258' is connected by an insulating coupler 380 to a shaft 392 to which is secured a coil 394 which forms with the stationary coil 396 a variable inductance or reactance 331. 339 and 331 are so wound and connected, and so phased on their respective shafts, that as the reactance of one increases the reactance of the other simultaneously decreases.

The reactances 389 and 391 are so arranged with respect to the reactances 311 and 385, to

which they are connected in parallel by cables 398 and 400, that changes in the reactances 311 and 385, caused by displacement of the shafts H8 and 380, are compensated for by opposite changes in the reactances 339 and 391 as the shafts 258' and 392 are swung by the pen driver, section I12 to bring the pen I18 to the same.

position as the needle I38.

The gas discharge tube or Thyratron 402 has its cathode 484 connected to the mid-point of the secondary winding of the alternating current supply transformer 436. The plate 403 of the tube 432 is connected by wire M0 to one end of the pen driver coil I84, the other end of which is connected by lead M 2 to one end of the seconda y winding of the supply transformer 408. A resistor Ell is connected between the other end of the secondary winding of that transformer and the lead MS to the grid N3 of the tube 402. A grid resistor 32!! is interposed in this lead M8. The parallel connected reactances 385 and 389 are connected to the grid lead M5 by wire 422 and to the lead M2 by wire 24. The resistance 3 and parallel connected reactances 385 and 389 comprise a phase shifting circuit which impresses on the grid of the tube a voltage which varies in phase, with respect to the plate voltage, on variation in the resultant reactance of the parallel connected reactances 385 and 389. The resistance and reactance of this phase shifting circuit are so proportioned that the tube 482 fires at the mid-point or peak value of each positive half cycle of plate voltage when the shafts of the transmitter and the recorder are in the same angular position.

The coils of each of the variable reactances A second gas discharge or Thyratron tube 426 has its cathode 428 connected to the mid-point of the secondary of a supply transformer 430. The anode 432 is connected by wire 434 to one end of the pen driver coil I82, the other end of which is connected by lead 436 to one end of the secondary winding of the transformer 430. The resistor 438 is connected between the lead 440 to the grid 442 of the tube 428 and the other end of the secondary winding of the transformer 430. A resistor 444 is inserted in the grid lead 440. The parallel connected reactances 311 and 391 are connected by wires 446 and 448 to the grid lead 440 and lead 436. The resistor 438 and parallel connected reactances 311 and 391 also form a phase shifting circuit impressing on the grid of the tube 426 a voltage which varies in phase, with respect to its plate voltage. on change in the resultant reactance of the parallel connected reactances 311 and 391. The resistance 438 and these reactances are so proportioned that the tube 426 also fires at the peak value of positive plate voltage when the transmitter and recorder shafts are at the same angular position.

It will be evident that when the shaft I48 of the transmitter is displaced. the reactances 311 and 385 chance in opposite senses. Let it be assumed that the shaft I48 is displaced in such direction that the reactance 311 is decreased and the reactance 385 is increased. The decrease in the reactance 311 produces a shift in the phase of the grid voltage applied on the tube 426 relative to the plate voltage in such a direction that the tube 425 fires earlier than the instant when the peak value of positive plate voltage is at ained in each alternating-current cycle. Thus, the tube 426 is rendered conductive for a longer period in each cycle, determined by the extent of the phase shift between grid and plate voltages. than would be the case if the testing and recorder members occupied corresponding angular positions. Conversely, the increase in the reactance 385 causes the phase of the grid voltage impressed on tube 402 relative to the anode volta e to be shifted in such a direction that tube 402 fires later in the cycle, after the positive plate voltage is past its peak value. Thus, tube 402 is rendered conductive for a shorter period during the alterhating-current cycle than would norma ly be the case. As a result of the foregoing operation, the average current supplied to the driver coil I82 is increased and the average current supplied to the driver coil W4 is decreased, causing the indicator shaft 200 to move and to continue in motion so long as the unbalance of driving forces exerted by the respective coils I82 and H4 persists. The pen I18 is thereby swung in a direction to follow the movement of the needle I66 to cause the reactance 389 to decrease and the reactance 391 to increase. The movement of the pen is continued until the change caused in the reactance 389 is just sufficient to compensate for the change caused in the reactance 385 so that the phase of the grid voltage impressed on the tube 402 is advanced and the tube again fires at the peak value of positive plate voltage. This move merit of the pen also causes the reactance 391 to increase sufhciently to compensate for the change in the rcactance 311 and to retard the phase of the grid voltage impressed on the tube 426 so that this tube also again fires at the peak value of positive plate voltage.

In the form of the invention shown in Figure 14, the transmitter H16" has a shaft I48" which corresponds to the shaft 148 of the form shown in Figures 5 to 12 and to the shaft I48 of the form shown in Figure 13. This shaft has secured to it, by means of arms 450 and 452 which are insulated from the shaft, electrodes 454 and 458 of variable condensers or reactances 458 and 460. The electrodes 454 and 458 cooperate with stationary electrodes 462 and 484 of the condensers 458 and 450.

The recorder I12 has secured to its shaft 253", which corresponds to the previously described shafts 258 and 258', movable electrodes 464 and 468 of variable condensers or reactances 410 and 412. These electrodes cooperate with the stationary electrodes 414 and 416 of the variable condensers 410 and 412. The gas discharge tubes 402 and 426 are connected to the supply transformers 406 and 430 in the same manner as described with respect to Figure 13. In this case, however, the resistances 4H and 438 are connected in the grid-to-plate circuits, and the parallel connected condensers 458 and 410 are connected in the grid-to-cathode circuits.

The resistances and capacitive reactances are proportioned to cause the tubes to fire at the peak value of positive plate voltage when the needle IE6" and the pen I18" are at the same angular position.

Displacement of the shaft I48" of the transmitter causes the grid voltages of the tubes 402 and 426 to be shifted in phase in opposite sense so that one tube fires earlier and the other fires later in its positive half cycle of plate voltage. The extent of this phase shift, and hence the change in the average current in each tube, depends, of course, on the extent of displacement of the shaft I48" relative to the shaft 258".

It will be evident that the response sensitivity of the recorder depends on the angle through which the transmitter shaft must be displaced in order to initiate movement of the recorder pen shaft and that the speed of response of the telemeter system depends on (1) the speed of response of the control unit and (2) the speed of response of the pen driver section of the recorder.

Since the tubes of the control unit fire, when the system is balanced, at substantially the peak value of plate voltage, and displacement of the transmitter shaft causes an increase in the current to one driver coil and a decrease in the current to the other driver coil, a very small displacement of the transmitter shaft is sufficient to initiate operation of the recorder pen shaft. Thus it has been found, in use, that a displacement of the transmitter shaft corresponding to a plunger displacement, of 2X10- inches is suflicient to cause operation of the recorder pen shaft.

The dynamically balanced, twin "voice coil construction of the pen driver section of the recorder and the simultaneous opposite change of the currents in the coils assure substantially instantaneous response of the recorder pen shaft to the control unit.

The speed of response of the tubes of the control unit depends on the frequency of the supply voltage. The speed of response of the tubes will be of minimum value when the displacement of the transmitter shaft occurs at the instant that the plate voltage is passing through zero and building up in a negative direction. When the transmitter shaft is displaced, one or the other of the tubes responds in the first half of its positive half cycle of plate voltage. Therefore, if the frequency of the supplied voltage is 60 cycles per second, the maximum response time is /50 o! a second. If the displacement occurs timing the positive half cycle of plate voltage, the control unit responds instantaneously, or within /240 of a second.

Where response within /240 of a second is required at all times, a second control unit of like construction may be employed. In such case, the second control unit may be connected to the transmitter and to the recorder in parallel to the first control unit, but connected to the supply line in opposed phase relation to the first control unit,

so that the tubes of the second control unit fire during the time that the plate voltage of the tubes of the first unit is passing through its negative half cycle. In that case, one of the four tubes of the two control units will respond within /240 of a second to any movement of the transmitter shaft. When two control units are employed, the grounded connection 302 will, of course, be eliminated.

By employing frequency changing or multiplying circuits in the power supply, the speed of response may be increased as desired.

It is apparent from the foregoing description that I have provided a novel telemetering apparatus in which rotary circuit elements (such as the coils I44 and 246, Fig. 5, variable inductors e11, 385, see and 391, Fig. 1a, or variable capacitors 458, 460, 410 and 412, Fig. 14) are interconnected by an electronic control circuit as I'll, Fig. 5, or the equivalent thereof in Figs. 13 and 14, in such manner that the position of a recording member as H8 is caused to correspond with the position of a testing member as T6. The electronic control circuit, as explained hereinabove, utilizes gas tubes which respectively control the flow of current through the opposed driving coils as 182 and I84 that actuate the recording member. When the aforesaid rotary circuit elements respectively associated with the testing and recording members are in corresponding angular positions, the gas tubes have substantially equal firing periods. However, lack of correspondence in the angular positions of these rotary elements causes the grid voltages applied to the gas tubes to change in opposite senses (that is, vary oppositely in magnitude or phase) so that the firing periods of the gas tubes no longer are equal. This produces an unbalance in the opposing forces exerted by the driving coils upon the recording member, causing the recording mernher to assume a new position to restore the dynamic balance. It will be understood that while the invention has been shown as applied specifically to a surface testing and recording apparatus, it is capable of being adapted to a variety of uses. Thus, the testing member may be regarded broadly as a sensing device for ascertaining a measurable quantity; while the recorder is, in its broad aspect, a register to indicate the sensed quantity.

While certain specific structural details have been disclosed to illustrate certain embodiments of the invention, it will be apparent that other modifications and changes may be made without departing from the spirit and scope of the appended claims.

What I claim is:

1. In an electrically operated position tester and recorder which includes a movable testing. member, a movable recording member, a telemetric transmitter having a rotary electric circuit element mechanically coupled to the testing member, a telemetric receiver having a rotary electric circuit element mechanically coupled to the recording member, and means for energizing iii) said transmitter and said receiver from the same source of reference alternating-current voltage, the combination comprising a gas tube, means electrically coupling said gas tube to the reference voltage source, means electrically coupling said gas tube to both said rotary elements in opposed phase relation, whereby the firing time of said gas tube in each cycle of the reference voltage depends upon the angular position of the receiver rotary element relative to the transmitter rotary element, and a pair of opposed driving elements for-said recording member, means for energizing one of said driving elements, the other of said driving elements being energized in response to said gas tube for at least a part of the energized period of said first named driving element to produce correspondence in the angular position of said receiver rotary element with respect to said transmitLer rotary element responsive to a difference between the conductive period of said gas tube and a predetermined portion of each cycle 01 the reference voltage.

2. In an electrically operated position tester and recorder which includes a movable testing member, a movable recording member, a telemetric transmitter having a rotary electric circuit element mechanically coupled to the testing member, a telemetric receiver having a rotary electric circuit element mechanically coupled to the recording member, and means for energizing said transmitter and said receiver from the same source of reference alternating-current voltage, the combination comprising a pair of gas discharge tubes each having a control electrode, means connecting both said rotary elements to the control electrodes of said tubes in opposed phase relation in a common control circuit, means electrically coupling both said gas tubes to the reference voltage source with the same polarity, and a pair of opposed electric driving elements for said recording member controlled respectively by said tubes, whereby there is produced a not effective driving force on said recording members so long as said rotary elements are in dissimilar angular positions.

3. In an electrically operated surface tester and recorder which includes a movable testing member, a movable recording member, a teleme'tric transmitter associated with the testing member, a telemetric receiver associated with the recording member, and means whereby said transmitter and said receiver are energized by a source of reference alternating-current voltage, the combination comprising first and second gas tubes, each having a cathode, an anode and a control grid, first and second variable reactors in said transmitter, third and fourth variable reactors in said receiver, means connecting the grid and cathode of said first gas tube to said alternating current source and to said first and third reactors in parallel, means connecting the grid and cathode of said second gas tube to said second and fourth reactors in parallel, means connecting the anodes and cathodes of both said gas tubes to said alternating current reference voltage source, whereby the alternating current grid voltages of said tubes are oppositely controlled as to phase in relation to the alternating current anode voltages depending upon the angular position of the receiver rotary element relative to the transmitter rotary element, and a pair of opposed electric driving elements mechanically coupled to said recording member and controlled respectively by said first and second gas tubes to produce correspondence in the angular position of said receiver rotary element with respect to said transmitter rotary element in response to a difference in the respective conducting periods of said gas tubes during each cycle of the reference voltage.

4. The combination set forth in claim 3, wherein said reactors comprise variable inductors.

5. The combination set forth in claim 3, wherein said reactors comprise variable capacitors.

6. An electrically operated registering device comprising an axially movable indicator shaft, means providing a stationary magnetic field around said shaft, and a pair of separate axially movable coils disposed on and mechanically connected to said shaft, said coils being respectively adapted when individually energized to move said shaft in opposite directions.

7. An electrically operated registering device comprising an axially movable indicator shaft, means providing a stationary magnetic field around said shaft, a pair of separate axially movable coils disposed on and mechanically connected to said shaft, said coils being adapted when individually energized to move said shaft in opposite directions, and means responsive to a variable quantity to be registered for supplying electric currents of unequal values to said coils as an incident to, and determined by, variations in the value of such quantity.

8. In a position tester and recorder, alternating-current power supply means, means including a position responsive member for supplying alternating current varying in phase relative to said alternating-current power supply means and in magnitude with the position of said member, a recorder having a movable recorder member, and opposed driving elements connected to said recorder member, a pair of gaseous discharge tubes each having a controlled circuit and a control circuit, one of said driving elements being connected in the controlled circuit of one of said tubes and the other of said driving elements being connected in the controlled circuit of the other of said tubes, said controlled circuits of the tubes being connected to said power supply means in parallel, a pair of supply transformers having their secondaries in the control circuits of said tubes, said transformers having their primaries connected'in series with said variable alternating current supply means and being phased to supply control voltages of substantially opposite phase to said tubes thereby to vary the thing period of said tubes in opposite senses in accordance with each change in the position of said position responsive member.

9. In a telemetric registering system, a telemetering transmitter including a variable ratio transformer, a telemetering receiver including a variable ratio transformer, a pair of gaseous discharge tubes each having a control circuit and a controlled circuit, means connecting the variable ratio transformers of the transmitter and the receiver in series opposition to the control circuits of said tubes whereby to vary the firing periods of said tubes in opposite senses, said telemetering receiver having opposed electrically operable driving elements, and means connecting one of said driving elements in the controlled circuit of one of said tubes and the other driving element in the controlled circuit of the other tube.

10. The combination in on electrical measuring and registering system of an indicator having a movable indicator member, opposed driving elements connected to said member, a pair of gaseous discharge tubes having output circuits in which said driving elements are connected and each having a control member, a variable ratio transformer having a movable ratio control element connected to said indicator member, a second variable ratio transformer having a movable ratio control element responsive to a quantity to be indicated, means for connecting the primaries of said transformers to a source of alternating current, and means for connecting the secondaries of said transformers in series opposition to the control members of said tubes to vary the control voltages impressed on said tubes in opposite phase.

ARTHUR F. ECKEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 363,333 Hammer May 17, 1887 473,539 Weston Apr. 26, 1892 812,196 Evershed Feb. 13, 1906 1,215,867 Romain Feb. 13, 1917 1,970,442 Whittl-:uhns et al. Aug. 14, 1934 2,085,128 Staege June 29, 1937 2,088,659 Moseley Aug. 3, 1937 2,165,510 Rosene July 11, 1939 2,206,852 Poupitch July 2, 1940 2,261,093 Poupitch Oct. 28, 1941 2,270,991 Bagno Jan. 27, 1942 2,357,524 Klepp Sept. 5, 1944 2,385,641 Peterson Sept. 25, 1945 2,420,539 Hornfeck May 13, 1947 

